MASTIGOPHORA 25 



and strands. The colony is in some cases very complex with division 

 of labor among the different individuals. 



The Mastigophora have been known from the earliest period of 

 the study of microscopical animals under the general name of Flagellata, 

 and are still so known in many textbooks. The name Mastigophora 

 was given the group by Biitschli in 1883. The animals live in both 

 fresh and salt water, and many are parasites in the higher animals, 

 being often the cause of disease. Large numbers closely resemble 

 plants and many are on the border line between animals and plants. The 

 class contains 3 subclasses with about 350 species. 



Key to the subclasses of Mastigophora: 



Oj Small Mastigophora with a definite anterior and posterior end, at one or the 

 other of which are 1 or more flagella 1. FLAGELLIDIA 



a a Mastigophora with usually 2 flagella, 1 anterior and 1 transverse in posi- 

 tion 2. DlNOFLAGELLIDIA 



o s Large marine Mastigophora with parenchymatous protoplasm. 



3. CYSTOFLAGELLIDIA 



SUBCLASS 1. FLAGELLIDIA. 



Body with a well-defined cuticula which gives it a definite shape, 

 the cuticula in some forms, however, being so thin that changes in shape 

 often take place; pseudopodia formed in certain forms; many flagel- 

 lates are protected by external coverings of jelly, chitin, silica or 

 cellulose; 1, 2 or several flagella extend from one end of the body, 

 usually the forward; in the Choanoflagellida, however, the single flagel- 

 lum is at the hinder end and is surrounded at its base by a collar: 8 

 orders, in which are included the great majority of flagellates, very 

 many containing chromatophores and being apparently allied to plants. 



Key to the orders of Flagellidia : 



a t Body colorless, often more or less amreboid, and with one or more flagella. 

 &! Body spiral with or without flagellum, and more or less like bacteria. 



1. SPIBOCHETIDA 

 fc a Body not spiral. 



Cj One flagellum with collar present 3. CHOANOFLAGELLIDA 



C 2 No collar present. 

 di Body with indistinct cuticula, often more or less amreboid. 



! Body elongate with undulating membrane 5. TBYPANOSOMATIDA 



e-t No undulative membrane present. 

 /! Two or more flagella, one directed forward, the other trailed behind. 



4. HETEBOMASTIGIDA 

 / 2 Flagella always directed forward. 



fh One or two flagella ; body usually more or less amreboid . . 2. MONADIDA 



2 Three or more flagella 6. POLYMASTIGIDA 



dt Body with distinct cuticula 7. EUGLENIDA 



Oj Body usually either yellow or green, often colonial. 



Z>! Body with distinct cuticula, and usually solitary 7. EUGLENIDA 



6 2 Body usually with a hyaline, gelatinous or cellulose house ; colonial. 



8. PHYTOFLAGELLIDA 



